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A heartfelt message written in the snow atop a hospital parking garage Monday was the work of a 14-year-old boy and his family, who were sending the message to his mother after she was diagnosed with leukemia. (Published Tuesday, Feb. 11, 2014)

William Hart was on his way to visit his mother at Rush University Medical Center in Chicago when he came up with the idea of writing her a message in the snow.

PHOTOS: Chicago's Season Of Snow

He and his father stamped out the words "Hi Mom," with a smiley face in the "O" of Mom, in the snow on top of the hospital's parking garage, which was visible from his mother's room.

"We kind of just shuffled our feet and made the words," William said.

He called his mom and told her to look out her window, where he stood waving in the middle of the snowy note.

"I looked out the window and saw the message and this little body waving all around with his dad and his uncle," Shari Hart said. "It's more than just I love you mom, it's a show of love that goes way beyond words,"

After the family's visit, William and other members of his family decided to write a message to all the patients at the hospital.

They began to stomp out the words "God Bless U All" but ran out of room, leaving just the words "God Bless U."

Angela Washek, a surgical intensive care unit nurse at the Chicago hospital, said she saw four people on the garage's roof at 1 a.m. Monday and quickly realized they were writing a message.

"It wasn't that difficult, it didn't take that long and we noticed people looking down on us as we were doing it, and that made it kind of special," Shari's husband, Tim, said. "It was just fun, we were just playing in the snow and fantastic, people are getting excited about it, something simple,"

A photo of the snow-stamped note was posted to the hospital’s official Twitter account Monday, and was also sent to NBC Chicago.